• I've dockerized my django web app.
• Whenever i run "docker-compose up" everything works fine and it opens locally
• But when i run "python manage.py runserver" it pops up an error mysql.connector.errors.DatabaseError: 2005 (HY000): Unknown MySQL server host 'db' (2)
• This is the same error it is showing when i deployed it to azure
• When docker-compose up runs without error locally and the web app works well

here is my docker-compose.yml file

services:
db:
  image: mysql
  ports:
    - '3306:3306'
  environment:
     MYSQL_DATABASE: 'app'
     MYSQL_USER: 'root'
     MYSQL_PASSWORD: 'aspilos'
     MYSQL_ROOT_PASSWORD: 'aspilos'
web:
  build: .
  command: python manage.py runserver 0.0.0.0:8000
  volumes:
    - .:/aspilos
  ports:
    - "8000:8000"
  depends_on:
    - db

Here is my utils.py file

import mysql.connector
mydb = mysql.connector.connect(
  host="db",
  user="root",
  passwd="aspilos",
  database="aspilos_log",
  auth_plugin="mysql_native_password"
) 
 mycursor = mydb.cursor()
 mycursor.execute("SELECT CONCAT('+', PHONE_NUMBER) FROM category2")
 results = mycursor.fetchall()
 for i in zip(*results):
 number = list(i)
 number1 = '+2348076548894'
 print (number)

Here is my settings.py file

DATABASES = {
 'default': {
   'ENGINE': 'django.db.backends.mysql',
   'NAME': 'app',
   'USER': 'root',
   'PASSWORD': 'aspilos',
   'HOST': 'db',
   'PORT': '3306',
  },
}